Mulching lawn mower blade and housing assembly

ABSTRACT

A rotary mulching lawn mower is provided having an annular housing forming a toroidal internal cutting chamber in which is oriented a blade having a central axis for rotation. The blade has a series of blade portions extending radially outward from the central axis each having an end portion extending into the toroidal internal cutting chamber. The blade end portion directs cut grass upward into the cutting chamber. Each blade has an intermediate portion located between the central axis and the end portion having a substantially flat surface lying in a plane generally perpendicular to the axis of rotation. The intermediate portion is provided with a radially extending rib located intermediate the leading and trailing edge portions of the blade having a slope projecting downwardly out of the plane for directing cut grass into the lawn upon rotation of the blade. The lawn mower of the preferred embodiment is driven by a battery powered electric motor.

TECHNICAL FIELD

This invention relates in general to machines for mulching grass. Moreparticularly, this invention relates to rotary type lawn mower cuttingelements which are rotated in a horizontal cutting plane for severinggrass at a predetermined height above the ground. Still further, itrelates to lawn mower cutting elements of the above type, where theprime motive source is an electric motor.

BACKGROUND OF THE INVENTION

Motorized lawn mowers of various types are well known for cutting grassor similar vegetation. These motorized lawn mowers generally include ahousing having a cutting chamber, a rotatable cutting blade which isrotated in the cutting chamber and some type of motive means foreffecting rotation of the cutting blade. Typical lawn mowers have beendesigned to incorporate one or more grass discharge ports where the cutgrass is discharged by the operation of the cutting blade. The grassclippings are then deposited on the lawn and raking or gathering up theclippings is necessary when the grass is long. Alternatively, a bagattachment can be connected to the discharge port to collect the grassas it is discharged from the lawn mower.

As an alternative to clipping discharge and bagging chute type lawnmowers, numerous types of mulching lawn mowers are disclosed in theprior art that do not require bagging or raking of the grass clippings.These chuteless lawn mowers cut the grass clippings to a fine mulchwhich is deposited directly onto the lawn.

It is ecologically advantageous to deposit the mulched grass particlesonto the lawn because they are a good nutrient source for the uncutgrass. The grass particles decompose quickly and do not contribute to abuild up of thatch as much as do longer length non-mulched clippings.Non-mulched clippings are often bagged and transported to landfills,contributing to the already significant solid waste disposal problems oflandfills.

Prior art mulching mowers utilize various systems for initially cuttingand recutting the grass clippings. Some systems utilize a toroidalchamber with a cutting blade that creates an air current for moving thecut grass clippings within the cutting chamber. The grass clippings arecut a plurality of times by the cutting blade before being depositedonto the grass. Other systems such as disclosed in U.S. Pat. No.4,951,449 to Thorud utilize a plurality of planar members which aredisposed along the inner wall of the cutting chamber. These planarmembers or "kickers" are utilized to deflect the grass clippings downinto the direction and through the cutting plane. The blade subsequentlydirects the grass clippings onto the lawn. Still further, other systemsutilize cutting elements with a plurality of cutting blades or memberswhich increase the cutting action of the cutting element.

Regardless of the mulching system used in the prior art, it should benoted that the retention of grass clippings within the cutting chamber,and the requirement for these grass clippings to be cut a plurality oftimes in the mulching process, imposes a greater load on the motivesource driving the blade than does a comparable non-mulching lawn mower.Thus, mulching lawn mowers utilizing electric motors as the prime motivesource are subject to unique problems because they have comparablylesser horsepower outputs than mulching lawn mowers utilizing internalcombustion engines.

Non-mulching chute type mowers generally have a tangential passage ofair that exits the discharge chute located on the housing. In contrast,chuteless mulching mowers have less internal air current created insidethe cutting chamber and are thus incapable of dissipating heat as easilyas chute type non-mulching mowers.

Thus it becomes apparent that mulching mower designs that utilizeelectric motors as the prime motive source for rotating the cuttingelement must be concerned with special problems associated with electricmotors. The overall drag that the cutting element produces in operationis of primary concern. Prior art mulching blade designs often includefoil members or sail members that are utilized to create upward aircurrents within the cutting chambers of the mulching mowers. These aircurrents are utilized to disburse and circulate the grass clippingsthroughout the cutting chamber to facilitate movement of the clippingswhich must be recut a number of times before being deposited on thegrass.

Conventional mulching blades are described in U.S. Pat. No. 3,085,386issued to Slemmons and U.S. Pat. No. 4,189,903 to Jackson, et al. Theutilization of large air foil or sail members on mulching mower bladesrequires increased horsepower to drive the blade as compared to regularlawn mower blades. The air resistance needed to create the air currentfor moving the clippings requires increased horsepower to rotate theblade.

An electric mulching mower is described in U.S. Pat. No. 4,318,268issued to Szymanis. The Szymanis patent discloses a chuteless rotarymulching lawn mower powered by an electric motor including a toroidalcutting chamber bounded by a concentric skirt wall. The mulching mowerblade disclosed in Szymanis includes an upwardly twisting portion forcreating an upward air flow during rotation of the blade. The Szymanismulching blade further includes a downwardly twisted portion forcreating a downward air flow for pulling grass clippings down throughthe cutting plan and onto the grass.

The Szymanis application refers to electric mulching mowers utilizingelectric motors. The Szymanis reference fails to address the significantobstacles posed in designing a battery powered electric mulching mower.Horsepower requirements of mulching mowers have in the past precludedimplementation of battery powered mulching mowers because of the sizeand weight characteristics of the attendant battery power sourcesrelative to the electrical energy requirements of mulching mowers.Battery sources possessing the electrical energy storage capacity largeenough to supply continuous energy to an electric mulching mower duringoperation in mulching an average lawn size were often too large and tooheavy for realistic consumer use.

SUMMARY OF THE INVENTION

Accordingly, the lawn mower of the present invention is provided with acutting blade having an end portion for cutting the grass and creatingan upward airflow upon rotation of the blade and an intermediate portionhaving a leading edge and a trailing edge lying in a plane generallyperpendicular to the axis of blade rotation. The blade is integrallyformed with an elongated rib projecting downwardly from the blade. Theelongated rib serves as a deflector forcing the cut grass in thedirection of the lawn upon rotation of the blade.

It is therefore an object of the present invention to provide a new andimproved cutting blade for an electric mulching mower which is capableof adequately mulching cut grass using an electric motor as the primemotive source.

It is a further object of the present invention to provide a new andimproved mulching blade for a battery powered electric mulching mowercapable of adequately mulching cut grass and extending the overallcutting time of the battery powered mower by reducing the horsepowerrequirements needed to drive the mulching blade.

It is a still further object of the present invention to provide a newand improved mulching blade which is capable of creating an air currentwithin the cutting chamber that forces the cut grass down through thecutting plane and onto the lawn.

It is an even further object of the present invention to provide a newand improved mulching blade and housing configuration that produces anair current that forces the grass clippings onto the ground and does notcreate a large drag or load on an electric motive source.

Still yet another object of the present invention is to provide a newand improved mulching blade and housing configuration wherein a mulchingblade has a relatively short end portion for creating an end currentthat forces the grass clippings upwardly and inwardly within a toroidalcutting chamber and an intermediate portion drawing the grass clippingsdown into the cutting plane.

Yet another object of the present invention is to provide a new improvedmulching blade and housing configuration wherein an elongate rib isdisposed along an intermediate portion of the cutting blade and is usedto draw grass clippings down onto the lawn and is also utilized tostrengthen the blade thereby allowing use of a thinner gauge materialwhich minimizes the horsepower required to drive the blade.

Other features and advantages of the invention will be set forth in, orapparent from, the detailed description of preferred embodiments of theinvention which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of the obverse side of a mulching lawn mowerconstructed in accordance with the present invention;

FIG. 2 is a partial cross sections view along section 2--2 of FIG. 1;

FIG. 3 is a top plan view of a cutting blade of the present invention;

FIG. 4 is a side elevational view of the cutting blade of FIG. 3;

FIGS. 5 and 6 are views along sections 5--5 and 6--6 of FIG. 3;

FIG. 7 is a fragmentary end view of the cutting blade of the presentinvention taken along section 7--7 of FIG. 4; and

FIG. 8 is a partial cross section view along section 8--8 of FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to FIG. 1, a lawn mower is indicated generally by thereference numeral 10. The lawn mower 10 comprises a housing 12, acutting blade 14, and a motive source for rotating the cutting blade.The preferred embodiment of the present invention utilizes an electricmotor and a battery power source. FIG. 2 shows an electric motor 16disposed above the housing 12 and a battery 66 and a switch 68. A driveshaft 18 extends down from electric motor 16 and extends throughaperture 20 of cutting blade 14. As shown in FIG. 2 an index washer 22is positioned above a blade spacer 24 which is disposed above cuttingblade 14. Cutting blade 14 is affixed to drive shaft 18 by the use ofblade retainer 26 and nut 28.

The cutting blade of the present invention has an axis of rotationdesignated by reference numeral 30 as shown in FIG. 2. Cutting blade 14is symmetrical in configuration about its center "C". The direction ofrotation of the blade in operation is shown by the arrow "D" in FIG. 3.The cutting blade 14 includes an end portion 32 and an intermediateportion 34. The length of end portion 32 is represented by "E" in FIGS.2 and 3. End portion 32 has a bevel 36 which forms a cutting edge 38.Intermediate portion 34 has a bevel 40 which form a cutting edge 42. Asshown in FIG. 5, the angle α of bevels 36 and 40 is preferably withinthe range of about 25° to 35°, with the preferred embodiment using anangle α of 30°.

In operation the cutting blade is rotated by the motive source with mostof the cutting action occurring at the end portion 32. Cutting edge 38initially cuts the grass as it comes under housing 12. Blade 14 has athickness ranging preferably from about 0.125 to 0.145 inches and isformed of a cold rolled steel SAE Grade 10B38.

A rib 44 is located intermediate leading edge 46 and trailing edge 48 ofintermediate portion 34. Elongate rib 44 has a first inclined surface 50and a second inclined surface 52 as shown in FIG. 5, and described inmore detail below. A sail member 54 is disposed opposite theintermediate portion on the end portion 32 of the blade 14 as shown inFIG. 3. Sail member 54 is formed by bending the rearward corner of theblade upward along a fold line oriented at an angle φ relative to theblade trailing edge, where φ is approximately 45°. Referring to FIG. 6,sail member 54 is disposed on end portion 32 such that angle β is in arange of about 40° to 50° with the preferred embodiment having an angleβ of 45°. End portion 32 of cutting blade 14 is offset from intermediateportion 34 as shown in FIG. 3, by angle γ. Angle γ is in a range ofabout 7° to 12° with the preferred embodiment having an angle of 10°.Sail member 54 is beneficial in providing an increased lift for thegrass clippings. It should be appreciated, however, that the blade canbe fabricated without a sail member. When the sail member is omitted,lift and mulching efficiency is reduced slightly, however, cutting timefor a given motor size and battery capacity is extended due to the lowerdrag.

The specific configuration of the cutting blade of the present inventiongreatly reduces the drag or load put on the motive source used to rotatethe blade but still operates effectively as a mulching blade. In thepreferred embodiment of the present invention, as shown in FIGS. 3 and4, end portion 32 is angled up from the plane of rotation of the bladeapproximately 10° as represented by angle "Δ" in FIG. 7. Angle Δ of endportion 32 creates an upward air flow upon rotation of the blade andthus directs grass cut initially by cutting edge 26 up into the topportion of the cutting chamber. In the preferred embodiment of thepresent invention, angle γ is in a range of about 8° to 10°.

The present invention, in operation, draws grass clippings down and intothe cutting edge 38 located on intermediate portion 34 by a downward airflow created by rib 44. Upon rotation of blade 14, rib 44 creates adownward air flow as represented by the arrows shown in FIG. 2. Thisdownward air flow directs the upwardly, inwardly directed grassclippings down through the cutting path a second time to be recut bycutting edge 38. The combination of the upward, inward air flow createdby the end portion 32 and sail member 54 and the downward air flowcreated by rib 44 facilitates an inward toroidal current of air andgrass clippings that effectuates the actual recutting and deposition or"mulching" of the grass clippings.

In contrast to mulching mower blades of the prior art, the mulchingmower blade of the present invention is a low profile blade whichcreates comparably less drag or load on the motive source driving theblade. This is particularly important when the motive source is anelectric motor with limited horse power ranges and even more significantwhen the electric motor is powered by an onboard battery power source.

As discussed above, mulching mowers in general require more horsepowerthan standard discharge mowers because of the added requirements ofcirculating and recutting the grass clippings before deposition of thegrass onto the lawn. This requirement for more horsepower posessignificant problems for electric mulching mower systems and even moresignificant obstacles for battery powered electric mulching mowers. Thepresent invention overcomes these obstacles by the use of a low profilemulching mower blade that effectively mulches cut grass while reducingthe load requirements necessarily required of the motive source utilizedto drive the cutting element. In addition, the mulching mower blade ofthe present invention is configured with an elongate rib that not onlyfunctions as a grass deflecting member upon rotation of the blade, butacts to strengthen the blade structurally. This structural reinforcementextends to the overall useful life of the mulching blade.

In the preferred embodiment of the mulching blade shown in FIGS. 3 and4, the length "E" of end portion 32 is approximately 17% of the length"L" of blade. A range of about 15% to 20% has been found to be effectivein mulching the grass clippings while keeping relative drag on thecutting blade to a minimum. This relatively small percentage of theoverall blade devoted to facilitation of the upward, inward air currentsneeded for the mulching process translates to a correspondingly smallamount of surface area disposed tangentially to the plane of rotation ofthe cutting blade. This small tangential surface area is advantageous indecreasing air resistance or drag upon rotation of the blade and adds tothe low profile characteristic of the mulching blade of the presentinvention.

Mulching blades of the prior art disclose sail members or air foilportions that range from 1/4 to 1/2 of the overall blade length. Inaddition, the sharply down-turned transitional portion of the blade 56disposed between intermediate portion 34 and end portion 32 shown inFIG. 4, adds to the overall low profile characteristics of the presentinvention. This sharply downturned transitional portion 56 creates lessdrag when the blade is rotated than a longer transitional portion.

Elongate rib 44 extends down from intermediate portion 34 and creates adownward air flow upon rotation of the blade that pulls the grassclippings through the recutting plane again and directs the grassclippings onto the lawn. Elongate rib 44 is comprised of first inclinedsection 50 and second inclined section 52. The angles of inclination offirst inclined section 50 and second inclined section 52 are configuredsuch that drag is reduced on the motive source upon rotation of theblade. The overall surface area on rib 44 tangential to the plane ofrotation is relatively minimal as compared to prior art bladeconfigurations with downward air flow creating members. Elongate rib 44extends on approximately 40-45% of the overall length of the blade tocreate a sufficient downflow upon rotation of the blade. The preferredembodiment of the present invention shown in FIG. 3 includes an elongaterib 44 which extends on 42% of the overall length of the blade.

In the preferred embodiment of the present invention, first inclinedsection 50 is disposed at an inclination angle θ to the cutting planeless than inclination angle λ of second inclined section 52 as shown inFIG. 5. The preferred embodiment of the present invention utilizes aninclination angle θ from the plane of rotation of the blade of 15°.Inclination angle λ of the second inclined surface from the plane ofrotation is 50°.

The low profile elements of elongate rib 44 are in direct contrast toprior art members that were used for creating a downward air flow. Priorart blade designs contained extending members for creating a sufficientdownward air flow to drag the grass clippings through the recuttingplane a second time but were not concerned with the relative horsepowerrequirements created by the blades on the motive sources. Internalcombustion engines typically had an abundance of horsepower to drive theblade.

In addition to the low profile characteristics of elongate rib 44, rib44 works to structurally strengthen cutting blade 14 reducing incidenceof fracturing of the blade in use. Because of this strengtheningfeature, the gauge of the material used to manufacture the blade can belessened. Manufacturing cutting blade 14 of a thinner gauge thus worksto further reduce the load put an electric motor source that can be usedto rotate the blade.

FIG. 2 shows a preferred embodiment of the present invention with thehousing 12 disposed above cutting blade 14. Housing 12 has an annularouter top wall portion 58 and a centrally disposed sloped inner top wallportion 60. Annular top wall portion 58 has an upwardly extendingarcuate cross-section 62. Sloped top wall portion 60 cooperates withannular top wall portion 58 to form a toroidal internal cutting chamber64.

FIG. 8 shows a preferred embodiment of housing 12 having an extendingcurved portion 66 and a connecting portion 68. Extending curved portion66 contacts the grass initially and acts to bend the grass prior tointroduction into toroidal cutting chamber 64. The grass passes underconnecting portion 68 and straightens momentarily before being cut bycutting edge 38 of end portion 32.

End portion 32 of cutting blade 14 is disposed below inner top wallportion 60. End portion 32 directs the grass clipping upwardly andinwardly toward annular top wall portion 58 as shown in FIG. 2.Intermediate portion 34 is disposed below inner top sloped wall portion60. As the grass is moved in an upwardly, inwardly direction within thetoroidal cutting chamber 48, the clippings are drawn down through thecutting path of the rotating blade 12 and pushed onto the lawn byelongate rib 44 as shown in FIG. 2. The direction of the grass clippingsand air currents is represented by the direction of the arrows shown inFIG. 2, within toroidal cutting chamber 64. The combination of thecutting blade 14 and the toroidal cutting chamber 64 configured as inthe present invention creates internal toroidal air currents that carrythe grass clippings through the mulching process.

The cutting blade and toroidal cutting chamber, in combination, work toreduce the overall load imposed on the motive during the mulchingprocess. Annular outer top wall portion 58 and inner sloped top wallportion 60 act as deflectors or fixtures for the cut grass clippings tocontact and rebound off from as the toroidal internal cutting chamberair currents created by the rotation of the mulching mower bladetransport and direct the grass clippings through the mulching process.This again further reduces the horsepower requirements of the motivesource, and in the case of a battery powered electric mulching mower,extends the cutting time of the mower.

Referring to FIG. 2, the preferred embodiment of the present inventionutilizes a battery 66 and a switch 68 to energize electric motor 16. Asstated previously, configuration of the mulching blade 14 and thehousing 12 act to reduce the overall load on the electric motor 16 inoperation. Electric motor 16 is a permanent magnet 24 volt DC motorhaving a maximum output falling within the range of 1 to 2 horsepowerand most preferably, 1.5 horsepower. The operation of the motor iscontrolled by a conventional on/off relay type switch which also servesas a blade break as is well known in the art. Battery 66 is preferablythe sealed lead acid type commonly used in the industry today. Thebattery energy storage capacity is preferably within the range of 10 to20 amp powers and most preferably 15 amp powers. The high efficiencymulching blade designed in the present invention enables a relativelysmall battery to be utilized for a given blade diameter and moweroperating time.

The reduction in overall load that the electric motor 16 is subjected toallows for extended cutting time utilizing a battery source. Theextension of operational cutting time enlarges the overall commercialmarket for the mulching mower of the present invention. Consumers withlawns of various areas can utilize the mower of the present inventionwith less concern for the eventual exhaustion of battery power used tooperate the mower. The mulching mower of the present invention equippedwith an 18" blade, is capable of cutting the lawn of a house situated ona half acre lot on a single battery charge provided the grass is not wetand is not excessively long. Mulching mowers of the present inventionhaving a high efficiency blade can cut the vast majority of typicallawns on a single battery charge making battery operated lawn mowerspractical in many situations where gasoline powered lawn mowers are theonly practical previous lawn cutting alternative.

While this invention has been described in detail with particularreference to preferred embodiments thereof, it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention as described and defined in the appended claims.

What is claimed is:
 1. A cutting blade for use in a rotary mulching lawnmower wherein the blade is adapted for rotation about an axis ofrotation generally perpendicular to the lawn for cutting grass or thelike such blade comprising:a plurality of blade portions extendingradially from said axis, each blade portion having an end portion, saidend portion having means for cutting grass and means for generating anupward air flow directing the cut grass in a direction away from thelawn upon rotation of the blade; and an intermediate portion between theaxis of rotation of said blade and said end portion, said intermediateportion lying in a plane of rotation generally perpendicular to the axisof rotation of said cutting blade, said intermediate portion having aleading edge and a trailing edge substantially in said plane of rotationand a radially extending rib projecting downwardly out of said plane ofrotation intermediate said leading and trailing edges, said rib forminga deflector directing the cut grass in a direction towards said lawnupon rotation of the blade.
 2. The cutting blade of claim 1 wherein saidleading edge has a bevel forming a cutting edge for recutting grass,said cutting edge extending along the radial extension of saidintermediate portion.
 3. The cutting blade of claim 1 wherein said ribis an integral part of said intermediate portion.
 4. The cutting bladeof claim 1 wherein said rib strengthens said intermediate portion ofsaid blade.
 5. The cutting blade of claim 1 wherein said end portion isshorter than said rib.
 6. The cutting blade of claim 1 wherein thelength of said end portion is about 17% of the length of said bladeportion.
 7. The cutting blade of claim 1 wherein the length of said ribis about 42% of the length of said blade portion length.
 8. The cuttingblade of claim 1 wherein said rib has a first inclined surface extendingtowards said leading edge and a second inclined surface extendingtowards said trailing edge, and the inclination of said first inclinedsurface to the plane of said intermediate portion is less than theinclination of said second inclined surface thereto.
 9. The cuttingblade of claim 8 wherein the inclination of said first inclined surfacefrom said plane of rotation is about 15°.
 10. The cutting blade of claim8 wherein the inclination of said second inclined surface to said planeof rotation is about 50°.
 11. The cutting blade of claim 1 wherein saidend portion comprises a surface angled about 10° from the plane of saidintermediate portion in a direction to generate said upward air flow.12. The cutting blade of claim 11 wherein said end portion includes asail member disposed at the end of said surface opposite saidintermediate portion, said sail member upwardly inclined from saidsurface at an angle of about 45°.
 13. In a rotary mulching lawn mower,the combination comprising:a housing having an annular outer top wallportion and a centrally disposed sloped inner top wall portion, saidannular top wall portion having an upwardly extending arcuatecross-section, said sloped top wall portion cooperating with saidannular top wall portion to form a toroidal internal cutting chamber;and a blade having a central axis of rotation, said blade comprising aplurality of blade portions rotatable in said internal cutting chamberabout said central axis of rotation of said blade, each blade portionhaving an end portion disposed below said annular top wall portion, saidend portion having means for cutting the grass and means for directingthe cut grass into said annular top wall portion in an upwardly andinwardly direction upon rotation of said blade, and each blade portionfurther having an intermediate portion located between said central axisof rotation of said blade and said end portion; said intermediateportion having a substantially flat surface lying in a plane generallyperpendicular to said axis of rotation of said blade, said intermediateportion having a leading edge and a trailing edge in said plane; andsaid intermediate portion further having a radially extending ribdisposed intermediate said leading edge and said trailing edge, said ribhaving a sloped wall portion projecting downwardly out of said plane toform a deflector directing the inwardly directed cut grass from saidtoroidal internal cutting chamber towards said lawn upon rotation of theblade.
 14. The combination set forth in claim 13 wherein said leadingedge has a bevel forming a cutting edge for recutting grass, saidcutting edge extending along the radial extension of said intermediateportion.
 15. The combination set forth in claim 13 wherein said rib isan integral part of said intermediate portion.
 16. The combination setforth in claim 13 wherein said rib strengthens said intermediate portionof said blade.
 17. The combination set forth in claim 13 wherein saidrib includes a first inclined surface extending toward said leading edgeand a second inclined surface extending toward said trailing edge, saidinclination of said first inclined surface to the plane of saidintermediate portion is less than the inclination of said inclinedsurface.
 18. The combination set forth in claim 13 wherein theinclination of said first inclined surface from said plane of rotationis about 15°.
 19. The combination set forth in claim 13 wherein theinclination of said second inclined surface to said plane of rotation isabout 50°.
 20. The combination set forth in claim 13 wherein said endportion comprises a surface angled about 10° from the plane of saidintermediate portion in a direction to generate an upward air flow fordirecting the cut grass into said annular top wall portion.
 21. Thecombination set forth in claim 13 wherein said end portion includes asail member disposed at the end of said surface opposite saidintermediate portion, said sail member upwardly inclined from saidsurface at an angle of about 45°.
 22. The combination set forth in claim13 wherein said blade is driven by an electric motor.
 23. Thecombination set forth in claim 22 wherein said electric motor isenergized by a battery power source.
 24. A mulching lawn mower forcutting grass comprising:an electric motor having a drive shaft; abattery power source for energizing said electric motor; a housing forsupporting aid electric motor having a toroidal internal cuttingchamber; a cutting blade having a central axis of rotation, said bladeaffixed to said drive shaft for cutting said grass and comprising aplurality of blade portions rotatable in said toroidal internal cuttingchamber about said central axis of rotation of said blade, each bladeportion having an end portion disposed within said toroidal internalcutting chamber, said end portion having means for cutting the grass andmeans for directing the cut grass in an upward and inward direction uponrotation of said blade, and each blade portion further having anintermediate portion located between said central axis of rotation ofsaid blade and said end portion; said intermediate portion having aleading edge and a trailing edge; and said intermediate portion furtherhaving a radially extending rib disposed intermediate said leading edgeand said trailing edge wherein said intermediate portion is asubstantially flat surface lying in a plane generally perpendicular tosaid axis of rotation of said blade, said rib projecting downwardly outof said plane to form a deflector directing the inwardly directed cutgrass from said toroidal internal cutting chamber toward said lawn uponrotation of said blade.
 25. A mulching lawn mower of claim 24 whereinelectric motor is a permanent magnet DC motor having an output withinthe range of one to two horsepower.
 26. A mulching lawn mower of claim25 wherein the battery power source is a rechargeable battery having anenergy storing rating in amp-hours between 8 to 12 times the motorhorsepower rating.
 27. A mulching lawn mower of claim 24 wherein saidhousing further comprises an outer top wall portion and an inner topwall portion cooperating to form said toroidal internal cutting chamber.28. The mulching lawn mower of claim 24 wherein said end portioncomprises a surface angled about 10° from the plane of said intermediateportion in a direction to generate said upward air flow.
 29. A mulchinglawn mower of claim 28 wherein said end portion includes a sail memberdisposed at the end of said surface opposite said intermediate portion,said sail member upwardly inclined from said surface at an angle ofabout 45°.
 30. A mulching lawn mower for cutting grass comprising:a DCelectric motor having a generally vertical drive shaft; a battery powersource for energizing said electric motor; a housing for supporting saidelectric motor, said housing defining a toroidal internal cuttingchamber concentric with said drive shaft and having an arcuate top wallportion and a centrally disposed downward inwardly sloped inner wallportion; a cutting blade having a central axis of rotation, said bladeaffixed to said drive shaft for cutting said grass and having aplurality of blade portions rotatable within said toroidal internalcutting chamber about said central axis, each blade portion having anend portion disposed within said toroidal internal cutting chamber, saidend portion having a sharpened leading edge for cutting the grass and asail member for directing the cut grass in an upward and inwarddirection toward said annular top wall portion and said centrallydisposed sloped inner wall portion upon rotation of said blade, eachblade portion further having an intermediate portion located betweensaid central axis of rotation of said blade and said end portion; saidintermediate portion having a sharpened leading edge, a trailing edge,and a radially extending deflector, wherein said cut grass is directedby said arcuate top wall portion and said sloped inner wall portiontowards said deflector wherein said deflector further directs the cutgrass from said toroidal internal cutting chamber toward said lawn uponrotation of said blade.
 31. A mulching mower for cutting grass as inclaim 30 wherein said deflector is a rib disposed intermediate saidleading and trailing edge.